1. Field of the Invention
The present invention relates to the field of bioremediation. More particularly, the present invention relates to an in situ bioremediation system and method thereof for biodegradation, detoxification and mineralization of toxic organic and inorganic compounds, especially dioxins and polychlorinated biphenyls, in a contaminated geologic setting.
2. Description of the Related Art
Waterway contamination, including contamination of both the water column and associated underlying sediments, is a widespread problem in the United States and around the world which can be attributed largely to the development of industry along such waterway systems. Historically, waterways, such as harbors, lakes, rivers, and estuaries, provided convenient sites for the growth of many types of industries due the convenience and availability of water-based transportation, power, and waste disposal options. Contamination of waterway sediments and water columns became widespread because of the unfortunate perception that the water was an endless sink for the deposal of industrial wastes. Today, while American industrial facilities continue to generate and dispose of approximately 7.6 billion tons of industrial solid waste each year, there are clearly more government regulations, monitoring and procedures in place to ensure the proper disposal and management of environmental risks to protect our waters, lands and natural resources. Nevertheless, further improvements in industrial waste management are needed and especially, there is a demand for eradicating, mitigating and managing hazardous waste contamination from yesteryear.
Historically, many industrial facilities were built on estuary-based geologic sites, including salt marshes, mudflats, shellfish beds and reefs. Estuaries are partially enclosed coastal bodies of water, having an open connection with the ocean, where freshwater from inland is mixed with saltwater from the sea. For example, Chesapeake Bay is an estuary. This system is one of the largest estuaries in the United States and was formed during the melting of the Pleistocene ice sheets. Fjords, or drowned glacial troughs, form similar types of estuaries, particularly in colder regions such as Norway, Alaska, New Zealand, and other glaciated, mountainous coastal regions. Salt marshes and lagoons found behind barrier beaches, such as along the south shore of Long Island, N.Y. and down faulted sections of the earth's crust, such as San Francisco Bay, are additional types of estuaries.
Estuaries represent one of the most sensitive and ecologically important habitats on earth. They provide sanctuary for many species of waterfowl, store and cycle nutrients for larval and juvenile marine life, and serve as breeding grounds for many desirable species of marine ocean fish. Further, estuaries, in particular salt marshes, are regarded as among the most productive ecosystems on the planet, producing more organic matter per unit area than most forests, grasslands, and cultivated fields. As a result of their high productivity and interactions with the coastal ocean, salt marshes provide numerous societal benefits, including habitat for commercially harvested marine and estuarine biota and a natural filter for nutrients, pollutants and sediments from the water column. In addition, estuary-based geologic sites commonly provide excellent harbors. Indeed, most of the large ports in the United States, for example, New York, Philadelphia, Baltimore, Mobile, Galveston, Seattle, and San Francisco, are located in estuaries.
The development, however, of high-density population centers near these ports has caused deleterious effects on estuary environments that can destroy the very properties of the estuary that made development of those regions possible. Human impact on estuaries includes reclamation of tidal land by filling, pollution from sewage, solid waste, industrial effluent and hazardous wastes, and hot water, increased sedimentation filling the estuary, and alteration of the salinity of estuarine waters by withdrawal or increased influx of freshwater. Increasingly, federal and state governments are passing legislation to protect estuarine environments however, such environments are still faced with many past and present environmental risks posed by the industrial world.
One notorious and highly contaminated geologic site formed as a result of industrial waste activities is the Passaic River in New Jersey. The contamination in the Passaic River include high levels of dioxins and other contaminants in the sediments as a result of years of discharge of industrial effluents, sewer discharge and wastewater discharge by industries, such as, Diamond Shamrock which was linked to the production of Agent Orange, a dioxin-containing herbicide used by U.S. forces during the Vietnam War to expose forested areas.
The term dioxin refers to a family of halogenated organic compounds, the most common consisting of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzodioxins (PCDDs), are regarded as some of the most toxic compounds on the planet and are linked to a variety of diseases, including cancer, developmental abnormalities in tooth enamel, negative impact on immune system function, endometriosis, birth defects, and diabetes. More in particular, diseases associated with dioxin exposure are chloracne, soft tissue sarcomas, Hodgkin's disease, and non-Hodgkin's disease. Diseases with limited evidence of an association with Agent Orange are respiratory cancers, prostate cancer, multiple myeloma, Porphyria cutanea tarda (a type of skin disease), acute and subacute transient peripheral neuropathy, spina bifida, Type 2 diabetes, and acute myelogenous leukemia found only in the second or third generation. Diseases with inadequate or insufficient evidence of an association are hepatobiliary cancers, nasal or nasophargyngeal cancers, bone cancer, female reproductive cancers, renal cancer, testicular cancer, leukemia, spontaneous abortion, birth defects, neonatal or infant death and stillbirths, low birth weight, childhood cancers, abnormal sperm parameters, cognitive neuropsychiatric disorders, ataxia, peripheral nervous system disorders, circulatory disorders, respiratory disorders, skin cancers, urinary and bladder cancer. Diseases with limited or suggestive evidence of no association are gastrointestinal tumors such as stomach cancer, pancreatic cancer, colon cancer, and rectal cancer, and brain tumors.
The basic structure of PCDD/Fs includes two benzene rings joined by either a single (furan) or a double oxygen bridge (dioxin). Chlorine atoms are attached to the basic structure at any of 8 different places on the molecule, numbered from 1 to 10. There are 210 different PCDD/F congeners, comprising of 75 PCDDs and 135 PCDFs. The toxicity of PCDD/Fs is dependent on the number and position of the chlorine atoms, wherein congeners having chlorines in the 2,3,7, and 8 positions have been observed to have toxicity. Out of the 210 PCDD/F compounds in total, only 17 congeners (7 PCDDs and 10 PCDFs) have chlorine atoms in the relevant positions to be considered toxic by the NATO/CCMS international toxic equivalent (I-TEQ) scheme. 2,3,7,8-Tetrachloro dibenzene-para-dioxin is the most toxic of the congeners.
Dioxins can bioaccumulate in tissues over time and thus, even small exposures may accumulate to dangerous levels. The toxicity of dioxins is thought to be linked to the similarity of these compounds to natural hormones. Like hormones, dioxins have the ability to pass through cellular membranes and bind to neural receptors. By doing so, a dioxin molecule can literally alter the genetic structure of the cell, creating new instructions that can interfere and disrupt the immune, neurological, and cellular systems. Dioxins are also capable of remaining in tissues for very long periods of time, a trait that enhances their toxicity. The body does not remove dioxins and thus, its effects can be ongoing and long-term. Moreover, unlike most other toxins, dioxins do not require a minimal dose to be harmful.
Dioxins are produced in a variety of industrial processes where organic material is burned in the presence of chlorine, including sources such as trash burn barrels, land application of sewage sludge, coal fired utilities, residential wood burning, metal smelting and diesel trucks, together which account for nearly 80% of dioxin emissions. In incineration processes, dioxins can also reform in the atmosphere above the stack as the exhaust gases cool through a temperature window of 600° C. to 200° C., however, new emissions control technologies now make this route a minor contributor to dioxin emissions. Dioxins are also generated in reactions that do not involve burning, such as bleaching fibers for paper or textiles, and in the manufacture of chlorinated phenols, particularly when reaction temperature is not well controlled. Affected compounds include the wood preservative pentachlorophenol, and also herbicides such as 2,4-dichlorophenoxyacetic acid (or 2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T).
The Environmental Protection Agency Dioxin Reassessment Report, incorporated herein in its entirety, is a comprehensive review of dioxin, its sources, and impacts on human and animal health. Other countries, including Australia, New Zealand, and the United Kingdom, also have substantial similar research. Tolerable daily, monthly or annual intakes have been set by the World Health Organization and a number of governments.
While research over the past two decades has produced a body of knowledge demonstrating bioremediation of toxic hydrocarbons, dioxins, metals, nitrogen-based compounds and other contaminants produced by industrial America and accumulated in our waterway sediments, water columns, and wetland environments, a full reversal or effective mitigation of this contamination will require new and dynamic approaches to restore contaminated sites such as the Passaic River. In particular, while bioremediation of contaminated waterways, sediments, soils, ground water sites, lakes, ponds, aquifers, wells, shore fronts, oceans and the like have been demonstrated in various approaches to varying degrees of success, there is a need to develop large-scale in situ bioremediation systems that target toxic organic and inorganic compounds, including dioxins and PCB's, that are effective at reducing, mitigating or removing sediment and water-column contaminants particularly in waterway and estuary systems. Such new approaches also advantageously should be integrated with improvements in waterway infrastructures, such as roadways, piers, and bridges, for facilitating positive economic effects to contaminated geologic sites. Further, such improved approaches should bring about positive restorative effects on estuary systems, such as the restoration of important salt marsh conditions and biota.
A bibliography of references is included at the end of the specification. The specification refers to these references by the first author's name and publication date. The references listed in the bibliography, to the extent they provide exemplary procedural or other details supplementary to those set forth herein, including both material or immaterial support, are specifically incorporated herein by reference.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.